It's your choice, it comes to preference. Being someone who plays sejuani a lot (or used to, I can clear fine early on, so scaling is nice for me to do more late game. If you wanted to focus on helping you early clears you can take flat ap. If you're still struggling take fury over sorcery and if that's still a problem, go into the utility tree and get cd reuction summoner spells. With the summoner spell cooldown reduction I would take this route: Blue > Gromp > Wolves (smite) > Raptors (smite) > Red > Scuttle(if needed) > Krugs. Just take scuttle whenever you're low and with the new plants, be sure to check if they're up, but be careful of the enemy jungler, guess where they started and compare your clear sped to theirs to guess where they are.

Hey, I'm glad you enjoyed it! I really just thought this was a really fun build that works, so I wanted to share it so others can play it too. Also I do think getting some tank items would be good, but I didnt include it since I titled this "full ap". She works really well as an ap off tank too, something like runic echos, liandry's into tank. Thanks for checking my guide out.